1. Field of the Invention
This invention is related to fuels, especially hydrocarbon fuels, and lubricants, especially lubricating oils, and, more particularly, to a class of anti-wear, anti-fatigue, and extreme pressure additives that are derived from dithiocarbamyl β-hydroxy fatty acid esters for such fuels and lubricants.
2. Description of Related Art
In developing lubricating oils, there have been many attempts to provide additives that impart anti-fatigue, anti-wear, and extreme pressure properties thereto. Zinc dialkyldithiophosphates (ZDDP) have been used in formulated oils as anti-wear additives for more than 50 years. However, zinc dialkyldithiophosphates give rise to ash, which contributes to particulate matter in automotive exhaust emissions, and regulatory agencies are seeking to reduce emissions of zinc into the environment. In addition, phosphorus, also a component of ZDDP, is suspected of limiting the service life of the catalytic converters that are used on cars to reduce pollution. It is important to limit the particulate matter and pollution formed during engine use for toxicological and environmental reasons, but it is also important to maintain undiminished the anti-wear properties of the lubricating oil.
This is a major concern as effective catalytic converters are needed to reduce pollution and to meet governmental regulations designed to reduce toxic gases such as, for example, hydrocarbons, carbon monoxide and nitrogen oxides, in internal combustion engine exhaust emissions. Such catalytic converters generally use a combination of catalytic metals, e.g., platinum or variations, and metal oxides, and are installed in the exhaust streams, e.g., the exhaust pipes of automobiles, to convert the toxic gases to nontoxic gases. As previously mentioned, these catalyst components are poisoned by the phosphorous, or the phosphorous decomposition product of the zinc dialkyldithiophosphate; and accordingly, the use of engine oils containing phosphorous additives may substantially reduce the life and effectiveness of catalytic converters. Therefore, it would be desirable to reduce the phosphorous content in the engine oils so as to maintain the activity and extend the life of the catalytic converter.
There is also governmental and automotive industry pressure towards reducing the phosphorous content. For example, United States Military Standards MIL-L-46152E at present require the phosphorous content of engine oils to be at or below 0.10 wt. %, while the ILSAC Standards defined by the Japanese and United States Automobile Industry Association at present require the phosphorous content of engine oils to be at or below 0.08 wt. %, with future phosphorous content being proposed to even lower levels. Accordingly, it would be desirable to replace or at least decrease the amount of zinc dialkyldithiophosphate in lubricating oils still further, thus reducing catalyst deactivation and hence increasing the life and effectiveness of catalytic converters while also meeting future industry standard proposed phosphorous contents in the engine oil.
In view of the aforementioned shortcomings of the known zinc and phosphorus-containing additives, efforts have been made to provide lubricating oil additives that contain neither zinc nor phosphorus or, at least, contain them in substantially reduced amounts. Illustrative of non-zinc, i.e., ashless, non-phosphorus-containing lubricating oil additives are the reaction products of 2,5-dimercapto-1,3,4-thiadiazoles and unsaturated mono-, di-, and tri-glycerides disclosed in U.S. Pat. No. 5,512,190 and the dialkyl dithiocarbamate-derived organic ethers of U.S. Pat. No. 5,514,189.
U.S. Pat. No. 5,512,190 discloses an additive that provides anti-wear properties to a lubricating oil. The additive is the reaction product of 2,5-dimercapto-1,3,4-thiadiazole and a mixture of unsaturated mono-, di-, and triglycerides. Also disclosed is a lubricating oil additive with anti-wear properties produced by reacting a mixture of unsaturated mono-, di-, and triglycerides with diethanolamine to provide an intermediate reaction product and reacting the intermediate reaction product with 2,5-dimercapto-1,3,4 thiadiazole.
U.S. Pat. No. 5,514,189 discloses that dialkyl dithiocarbamate-derived organic ethers have been found to be effective anti-wear/antioxidant additives for lubricants and fuels.
U.S. Pat. Nos. 5,084,195 and 5,300,243 disclose N-acyl-thiourethane thioureas as anti-wear additives specified for lubricants or hydraulic fluids.
U.S. Pat. No. 3,407,222 discloses the reaction of ammonium dithiocarbamates of the formula:
with epoxides of the formula
in which R1, R2, R5, R6, R7 and R8 are each hydrogen, alkyl, phenyl, naphthyl, cyclohexyl or phenylethyl; R3 and R4 are each hydrogen, alkyl; cyclohexy or phenylethyl, and wherein R1 and R2 as well as R3 and R4 taken together with the nitrogen atom in the above said dithiocarbomate salt form an heterocyclic N-moiety selected from the group consisting of pyrrolidino, piperidino and morpholino.
U.S. Pat. No. 5,019,284 teaches that alkylene oxides (epoxides) or epoxidized oils such as epoxidized soybean oil or related functionalized epoxides may be reacted with either sodium dihydrocarbyl dithiocarbamates or triethylammonium salts of dihydrocarbyl dithiocarbamates to form S-hydroxyalkyl N,N-dihydrocarbyl dithiocarbamates as generally described in the following equation:
where R1, R2, R3, R4, R5, and R6 are hydrogen, or C1 to C60 hydrocarbyl, and can optionally contain sulfur, nitrogen and/or oxygen. The subject S-hydroxyalkyl N,N-dihydrocarbyl dithiocarbamates are not used as lubricant additives. Rather they are further reacted with dihydrocarbyl hydrogen phosphonates to prepare hydrogen phosphonate dihydrocarbyl dithiocarbamates.
U.S. Pat. No. 5,126,063 teaches the preparation of borated reaction products of metal dithiocarbamates with epoxides, and the use of these borated additives in lubricants and greases.
U.S. Pat. No. 5,698,498 discloses a lubricating composition comprising a major amount of an oil of lubricating viscosity and (A) a minor amount of at least one hydroxyalkyl dithiocarbamate or at least one borate thereof, wherein the dithiocarbamate is derived from an amine other than an alkyl or alkenylsuccinimide.
U.S. application Ser. No. 10/062,161, (US 2003/0139301) filed Oct. 26, 2001, discloses reacting alkyl glycidyl thioethers with primary and/or secondary amines and carbon disulfide to produce dithiocarbamates that are antioxidants and wear inhibitors, and that can be used in low phosphorus lubricants as a partial replacement for ZDDP.
U.S. application Ser. No. 10/067,978 (US 2003/0211951) filed Feb. 8, 2002, discloses preparation of hydroxysubstituted dithiocarbamates of the formula (1) or (2):
wherein R1, R2, and R4, are alkyl, R3 is alkyl or H, X is O or S, and n=1 or 2. All of the exemplified epoxides have terminal epoxide groups, e.g. epoxidized α-olefins, glycidal ethers, glycidal thioethers, and styrene oxide. This patent further discloses a composition comprising a molybdenum source, a hydroxyl-substituted dithiocarbamate, and optionally a phosphorus source.
Trofimov, B. A. et. al, Zeitschrift fuer Chemie (1987), 27(1), 24-5 describes the addition of various molar amounts of ammonium dithiocarbamates to 1-(2-vinyloxyethoxy)-2,3-epoxypropane to form 2-hydroxyalkyl dithiocarbamates.
Zhang, J. et al., Wear, 1999 224(1) 50-55 describes the use of S-[2-S-(2-hydroxylpropyl)benzothiazole]dioctyldithiocarbamic acid ester as an additive in liquid paraffin.